[48.05] High Resolution Imaging Spectroscopy of Mars using HST/STIS during 1999 and 2001

We have used the Hubble Space Telescope (HST) and the Space
Telescope Imaging Spectrograph (STIS) instrument to perform
high resolution imaging spectroscopy of Mars during the 1999
and 2001 oppositions. Our 1999 observations were obtained
using the G750L grating, covering 530 to 1030 nm at 0.48
nm/channel. The STIS 0.2\arcsec slit was pushbroom-scanned
across the 16.2\arcsec diameter planet in 70 adjacent
steps , yielding a 3-dimensional image cube in 1021
wavelengths and at ~20\times80 km spatial resolution
per spectrum. This sequence was executed during four visits
spaced ~90{\circ} apart in Martian longitude on 1999
April 27, May 1, 6, and 7 (Ls=130{\circ} to
135{\circ}). Each slit image was calibrated to I/F and
map-projected to yield a coregistered data set covering
~75% of the surface of Mars. Our 2001 observations
utilized the same measurement strategy, but used the G430L
grating to cover shorter wavelengths (270 to 590 nm at 0.27
nm/channel). Because of the failure of the STIS side 1
electronics in May 2001, our measurements could not be
obtained as planned near opposition in June 2001. Instead,
we obtained our measurements once STIS side 2 was brought
online, during four visits on 2001 August 9, 10, 14, and
September 4 (Ls=211{\circ} to 227{\circ}). The
planet ranged from 16.0\arcsec to 13.0\arcsec diameter
over those dates, yielding spatial resolution and global
coverage comparable to that obtained in 1999.

A primary goal of our study is to search for absorption
features diagnostic of Fe2+ and Fe3+ minerals on
Mars, and to map their spatial distribution. Our 1999
results focus on weak variations in spectral properties
associated with albedo, geologic, and topographic
variations, and comparisons to results from HST/WFPC2
imaging and MGS/TES spectroscopy. Initial results from our
2001 observations, obtained during one of the largest global
dust storms of the last 30 years, focus mostly on the
analysis of atmospheric aerosol physical and UV
spectroscopic properties.